Embodiments of the present invention relate to a method of fabricating a cleaning wafer for cleaning a surface of a substrate support.
In the fabrication of semiconductors and displays, material is formed or deposited on a substrate, such as a semiconductor wafer or dielectric, by processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), ion implantation, oxidation and nitridation. The material formed on the substrate can also be etched to define features of electric circuits and devices. Such processes are generally performed in a process chamber in which a plasma may be generated. The substrate is supported during these processes on a substrate support, such as an electrostatic chuck. The electrostatic chuck typically comprises a dielectric having a support surface that covers an electrode to which a voltage is applied. The applied voltage generates an electrostatic force that holds the substrate securely on the support surface during processing. An example of an electrostatic chuck is described in U.S. Pat. No. 6,563,686 to Tsai et al, filed on Mar. 19, 2001 and assigned to Applied Materials, which is herein incorporated by reference in its entirety. Other support surfaces in the chamber can comprise the surfaces of lift pins and substrate transports. The chamber also typically has enclosure walls about the substrate support, a gas distributor and exhaust, and a gas energizer.
In the processing of substrates, process residues can deposit on the surfaces of process kit parts such as shields. The process residues may be, for example, process by-products generated by etching or depositing material on the substrate. These process residues can accumulate on support surfaces, such as a substrate receiving surface of an electrostatic chuck, by “flaking off” from components such as the process kit and onto the support surface. Also, occasionally particles of silicon from wafer breaks in other chambers can be transported via the substrate transport into process chamber, and onto the surface of the electrostatic chuck. These particles and residues on the surface of the electrostatic chuck are undesirable, because they can reduce the magnitude of the electrostatic chucking force between the chuck and substrate. The reduced chucking force can cause slipping of the substrate on the electrostatic chuck during processing, and non-uniformity in the substrate processing results. Also, weakly held substrates may allow leakage of backside heat transfer gas, which can lead to non-uniform temperatures across the substrates. In some cases, large particles on the electrostatic chuck can even prevent the processing of further substrates, and can require venting of the process chamber to manually wipe the particles from the surface of the electrostatic chuck, which undesirably increases the chamber downtime and the cost of ownership.
In one version of a cleaning process, the surface of the support is rinsed in a cleaning solution to dissolve and wash away any residues the surface. However, conventional cleaning solutions can often erode chuck surfaces. Also, such processes can often require removal of the electrostatic chuck from the chamber, and venting of the chamber to atmospheric pressure, which can result in undesirable chamber downtime.
In another version, a dummy wafer is used to remove residues from the surface of the electrostatic chuck, as described for example in U.S. Pat. No. 5,746,928 to Yen et al., filed on Jun. 3, 1996, which is herein incorporated by reference in its entirety. In this version, the dummy wafer is placed on the chuck in a process chamber, and a voltage is applied to the chuck. Once the voltage is turned off, the dummy wafer is removed from the chuck along with debris and contamination that adhere to the backside of the dummy wafer. However, as the strength of adhesion of particles to the hard backside of the dummy wafer is limited, this method often does not provide sufficient cleaning of particles from the chuck surface, and may be especially problematic in the cleaning of larger particles. Also, such dummy wafers can also contaminate surfaces that are being cleaned by rubbing of the wafer material onto the surfaces.
Yet another version of a cleaning method is described in U.S. Pat. No. 5,671,119 to Huang et al, filed on Mar. 22, 1996, which is herein incorporated by reference in its entirety. In this version, a soft, particle adherent sheet is affixed to a dummy wafer, for example by vacuum grease, to assist in removing contaminant particles from an electrostatic chuck in an etching chamber. However, while the particles may exhibit improved adhesion to the soft sheet over the bare surface of the dummy wafer alone; this method still does not provide satisfactory results for the cleaning of support surfaces. In particular, the soft sheet attached by vacuum grease may not be suitable for the cleaning of process chambers that are typically operated at an ultra-high vacuum, such as deposition chambers operated at less than about 10−7 barr (9.8×10−7 atm), as the vacuum grease can contaminate the chamber. Also, the sheet held by the vacuum grease may not operate well at higher temperatures above room temperature, such as those typically used in processing chambers. Furthermore, the loosely held sheet may not adequately adhere to the dummy wafer, and it may be difficult to de-chuck the dummy wafer without also de-laminating the sheet. The poorly held sheet of material may also not provide sufficient electrostatic chucking forces between the chuck and dummy wafer, such that the layer is only weakly pressed against the particles on the surface of the chuck. Also, in general, the dummy wafers can have high particle counts and large numbers of chemical impurities. These particles and impurities can contaminate the soft sheets, for example during transport of the dummy wafers in close proximity to each other in cassettes.
Yet another version of a cleaning layer is described in WO 01/94036 to Namikawa et al, published on Dec. 13, 2001, which is herein incorporated by reference in its entirety. In this version, a cleaning sheet has a cleaning layer comprising a polymer on a base material, and is attached to a conveying member such as a semiconductor wafer by an adhesive layer. However, this embodiment is also problematic, as the adhesive layer can generate contamination in the process chamber, and the multiple layers of material can reduce the electrostatic chucking force. One or more of the multiple layers can also slip or de-laminate from the semiconductor wafer during the cleaning process, resulting in a poorer clean of the support surface.